Postfix input methods and read-char

[Gautier Ponsinet <gautier@gautierponsinet.xyz>]

Hello everyone,

The following question is motivated by the avy package
(https://github.com/abo-abo/avy) which relies on read-char. How to
select a character without accent via read-char with an active "postfix"
input method?

An example, in emacs -Q:
- C-u C-\ french-postfix <Enter>
- M-: (read-char "Prompt: " t) <Enter>
- a

Here, the minibuffer waits for a possible accent (^ or `). How can I
enter a simple "a" without accent?

All the best,
Gautier.